Dataset Information

Isolation by Distance, Source-Sink Population Dynamics and Dispersal Facilitation by Trade Routes: Impact on Population Genetic Structure of a Stored Grain Pest.

ABSTRACT: Population genetic structure of agricultural pests can be impacted not only by geographic distance and the broader ecological and physical barriers but also by patterns related to where crops are produced and how they are moved after harvest. Stored-product pests, for instance, specialize in exploiting grains such as wheat and rice from on-farm storage through transportation to final processing at often geographically distant locations; therefore human-aided movement may impact their dispersal. Although stored product insects are associated with stored grain, they can also exploit resources in the surrounding environments so different ecological regions where the grain is grown and stored may also influence population structure. Here we used 1,156 SNP markers to investigate how geographic distance, ecological and agricultural variables can impact the genetic structure and gene flow of the stored food pest beetle Rhyzopertha dominica We found a substantial degree of admixture between weakly structured populations in the US. Ecological regions were more important in explaining R. dominica population structure than crop type, suggesting insect movement between wheat and rice grain distribution channels. We have also found a significant correlation between the genetic and geographical distance (i.e., isolation by distance). However, our modeling approach combining the ecological and management variables has highlighted the importance of the volume of grain received by a location in the dispersal dynamics of the pest. The first-generation migrant analysis offered additional supported to movement over great distances that are likely associated with grain movement. Our data suggest that a multitude of factors play small but significant parts in the movement dynamics of the pest. The beetles can take advantage of the source-sink dynamic of grain movement in the US, but also engage in a high rate of movement at the local scale. Understanding population structure for R. dominica will provide insights into the potential for local processes of adaptation and broader patterns of movement that will impact management programs and the potential for spread of resistance genes.

SUBMITTER: Cordeiro EMG

PROVIDER: S-EPMC6505152 | biostudies-other | 2019 May

REPOSITORIES: biostudies-other

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Isolation by Distance, Source-Sink Population Dynamics and Dispersal Facilitation by Trade Routes: Impact on Population Genetic Structure of a Stored Grain Pest.

Cordeiro Erick M G EMG Campbell James F JF Phillips Thomas T Akhunov Eduard E

G3 (Bethesda, Md.) 20190507 5

Population genetic structure of agricultural pests can be impacted not only by geographic distance and the broader ecological and physical barriers but also by patterns related to where crops are produced and how they are moved after harvest. Stored-product pests, for instance, specialize in exploiting grains such as wheat and rice from on-farm storage through transportation to final processing at often geographically distant locations; therefore human-aided movement may impact their dispersal. ...[more]

PMID: 30808690

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Project description:Introduction:Alliaria petiolata, an herbaceous plant, has invaded woodlands in North America. Its ecology has been thoroughly studied, but an overlooked aspect of its biology is seed dispersal distances and mechanisms. We measured seed dispersal distances in the field and tested if epizoochory is a potential mechanism for long-distance seed dispersal. Methods:Dispersal distances were measured by placing seed traps in a sector design around three seed point sources, which consisted of 15 second-year plants transplanted within a 0.25 m radius circle. Traps were placed at intervals ranging from 0.25-3.25 m from the point source. Traps remained in the field until a majority of seeds were dispersed. Eight probability density functions were fitted to seed trap counts via maximum likelihood. Epizoochory was tested as a potential seed dispersal mechanism for A. petiolata through a combination of field and laboratory experiments. To test if small mammals transport A. petiolata seeds in their fur, experimental blocks were placed around dense A. petiolata patches. Each block contained a mammal inclusion treatment (MIT) and control. The MIT consisted of a wood-frame (31 × 61× 31 cm) covered in wire mesh, except for the two 31 × 31 cm ends, placed over a germination tray filled with potting soil. A pan filled with bait was placed in the center of the tray. The control frame (11 × 31 × 61 cm) was placed over a germination tray and completely covered in wire mesh to exclude animal activity. Treatments were in the field for peak seed dispersal. In March, trays were moved to a greenhouse and A. petiolata seedlings were counted and then compared between treatments. To determine if A. petiolata seeds attach to raccoon (Procyon lotor) and white-tailed deer (Odocoileus virginianus) fur, wet and dry seeds were dropped onto wet and dry fur. Furs were rotated 180 degrees and the seeds that remained attached were counted. To measure seed retention, seeds were dropped on furs and rotated as before, then the furs were agitated for one hour. The seeds retained in the fur were counted. Results:For the seed dispersal experiment, the 2Dt function provided the best fit and was the most biologically meaningful. It predicted that seed density rapidly declined with distance from the point source. Mean dispersal distance was 0.52 m and 95% of seeds dispersed within 1.14 m. The epizoochory field experiment showed increased mammal activity and A. petiolata seedlings in germination trays of the MIT compared to control. Laboratory studies showed 3-26% of seeds were attached and retained by raccoon and deer fur. Retention significantly increased if either seed or fur were wet (57-98%). Discussion:Without animal seed vectors, most seeds fall within a short distance of the seed source; however, long distance dispersal may be accomplished by epizoochory. Our data are consistent with A. petiolata's widespread distribution and development of dense clusters of the species in invaded areas.

Dataset Information

Isolation by Distance, Source-Sink Population Dynamics and Dispersal Facilitation by Trade Routes: Impact on Population Genetic Structure of a Stored Grain Pest.

Publications

Isolation by Distance, Source-Sink Population Dynamics and Dispersal Facilitation by Trade Routes: Impact on Population Genetic Structure of a Stored Grain Pest.

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